The present invention relates to a method of manufacturing a corona discharge electrode, wherein an electrode core of at least partially electrically conductive material is coated with a dielectric layer. The invention also relates to a corona discharge electrode produced by the novel method.
It is known that adhesion of upper surfaces of materials is improved by the exposure to a corona discharge and in non-polar materials, for example the surface adhesion can be established only upon treatment by the corona discharge.
In order to perform such a surface treatment by means of a corona discharge it is necessary to provide a source of electric energy in the form of a high frequency, high AC voltage generator, and a corona discharge electrode energized by the generator and being provided with a dielectric coating on which during operation the desired corona discharge occurs.
In the course of surface treatment by means of conventional corona discharge electrodes, the dielectric layer which is important for a uniform distribution of the corona discharge, proved to be a weak point.
The corona discharge during the continuous surface treatment strains the dielectric layer of the electrode to a degree which depends on the particular production method. It has been proved that depending on the kind of the dielectric layer, a wear occurs after different time periods. The wear however, in each case takes effect with an undesired speed.
The following factors can be the cause of this wear:
Due to porosity of the dielectric material and due to the requirement for a-short-circuit safe structure of the dielectric layer the latter has hitherto been deposited with a relatively large thickness. Consequently, the efficiency of the known corona electrodes has been considerably impaired. Accordingly, due to the lower efficiency the conversion of electric corona to effective power per surface unit becomes disadvantageously low and also the obtained adhesion values of the treated material are lower.
This deficit can be compensated for only with an increased power of the generator and with increased size of the employed devices which conditions lead to excessive heat generation on the corona discharge electrode and to corresponding wear.
Altogether, the wear as well as the impaired efficiency during the surface treatment by the corona discharge due to the wear lead to increased manufacturing costs and to corruption of quality of the treated material.